restrict a string field to a certain character set in access:

validation rule: not like '*[!a-zA-Z(]*'
(character set matches all that are not in the list of valid ones, using regexp-like syntax).

order by a generated column in msaccess:

you must reissue all the expressions for the column. e.g. if you do

SELECT sqrt(bar) + 82 as blah from table order by blah;

it will need to be rewritten as

SELECT sqrt(bar) + 82 as blah from table order by (sqrt(bar) + 82)

don't ask why